The present invention relates generally to a small-format zoom lens, and more particularly to a zoom lens lending itself to compact electronic imaging systems having an electronic imaging device, such as digital cameras, and an electronic imaging system incorporating such a zoom lens.
So far, digital cameras or video cameras require high-quality yet low-cost optical systems like those used on common cameras. In addition, it is still desirable to rely on an optical system showing improved telecentricity on its image side to counteract decreases in the quantity of rim light. For instance, three-group zoom lenses set forth in Patent Publications 1 and 2 are known to be fit for electronic image pickup devices such as solid-state image pickup devices. These three-group zoom lenses are each made up of, in order from its object side, a first lens group of negative refracting power, a second lens group of positive refracting power and a third lens group of positive refracting power, wherein the first and second lens groups are moved from the wide-angle end to the telephoto end thereof for zooming purposes.
Patent Publication 1 JP-A 2003-15035
Patent Publication 2 JP-A 2001-318311
However, such three-group zoom lenses are now found to have some shortcomings such as difficulty in gaining sufficient telecentricity, unavoidable use of costly vitreous materials, or grave influences of decentration.
With such prior art zoom lenses, correction of chromatic aberrations at the second lens group is still unsuccessful, often causing reproduced images to have noticeable chromatic blurs due to the broad photosensitivity of an electronic image pickup device in long or short wavelength regions.